hadoop-common-project/hadoop-common/src/main/conf/hadoop-env.sh - hadoop - Git at Google

 #
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file
 # distributed with this work for additional information
 # regarding copyright ownership.  The ASF licenses this file
 # to you under the Apache License, Version 2.0 (the
 # "License"); you may not use this file except in compliance
 # with the License.  You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.

 # Set Hadoop-specific environment variables here.

 ##
 ## THIS FILE ACTS AS THE MASTER FILE FOR ALL HADOOP PROJECTS.
 ## SETTINGS HERE WILL BE READ BY ALL HADOOP COMMANDS.  THEREFORE,
 ## ONE CAN USE THIS FILE TO SET YARN, HDFS, AND MAPREDUCE
 ## CONFIGURATION OPTIONS INSTEAD OF xxx-env.sh.
 ##
 ## Precedence rules:
 ##
 ## {yarn-env.sh|hdfs-env.sh} > hadoop-env.sh > hard-coded defaults
 ##
 ## {YARN_xyz|HDFS_xyz} > HADOOP_xyz > hard-coded defaults
 ##

 # Many of the options here are built from the perspective that users
 # may want to provide OVERWRITING values on the command line.
 # For example:
 #
 #  JAVA_HOME=/usr/java/testing hdfs dfs -ls
 #
 # Therefore, the vast majority (BUT NOT ALL!) of these defaults
 # are configured for substitution and not append.  If append
 # is preferable, modify this file accordingly.

 ###
 # Generic settings for HADOOP
 ###

 # Technically, the only required environment variable is JAVA_HOME.
 # All others are optional.  However, the defaults are probably not
 # preferred.  Many sites configure these options outside of Hadoop,
 # such as in /etc/profile.d

 # The java implementation to use. By default, this environment
 # variable is REQUIRED on ALL platforms except OS X!
 # export JAVA_HOME=

 # Location of Hadoop.  By default, Hadoop will attempt to determine
 # this location based upon its execution path.
 # export HADOOP_HOME=

 # Location of Hadoop's configuration information.  i.e., where this
 # file is living. If this is not defined, Hadoop will attempt to
 # locate it based upon its execution path.
 #
 # NOTE: It is recommend that this variable not be set here but in
 # /etc/profile.d or equivalent.  Some options (such as
 # --config) may react strangely otherwise.
 #
 # export HADOOP_CONF_DIR=${HADOOP_HOME}/etc/hadoop

 # The maximum amount of heap to use (Java -Xmx).  If no unit
 # is provided, it will be converted to MB.  Daemons will
 # prefer any Xmx setting in their respective _OPT variable.
 # There is no default; the JVM will autoscale based upon machine
 # memory size.
 # export HADOOP_HEAPSIZE_MAX=

 # The minimum amount of heap to use (Java -Xms).  If no unit
 # is provided, it will be converted to MB.  Daemons will
 # prefer any Xms setting in their respective _OPT variable.
 # There is no default; the JVM will autoscale based upon machine
 # memory size.
 # export HADOOP_HEAPSIZE_MIN=

 # Enable extra debugging of Hadoop's JAAS binding, used to set up
 # Kerberos security.
 # export HADOOP_JAAS_DEBUG=true

 # Extra Java runtime options for all Hadoop commands. We don't support
 # IPv6 yet/still, so by default the preference is set to IPv4.
 # export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"
 # For Kerberos debugging, an extended option set logs more information
 # export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true -Dsun.security.krb5.debug=true -Dsun.security.spnego.debug"

 # Some parts of the shell code may do special things dependent upon
 # the operating system.  We have to set this here. See the next
 # section as to why....
 export HADOOP_OS_TYPE=${HADOOP_OS_TYPE:-$(uname -s)}

 # Extra Java runtime options for some Hadoop commands
 # and clients (i.e., hdfs dfs -blah).  These get appended to HADOOP_OPTS for
 # such commands.  In most cases, # this should be left empty and
 # let users supply it on the command line.
 # export HADOOP_CLIENT_OPTS=""

 #
 # A note about classpaths.
 #
 # By default, Apache Hadoop overrides Java's CLASSPATH
 # environment variable.  It is configured such
 # that it starts out blank with new entries added after passing
 # a series of checks (file/dir exists, not already listed aka
 # de-deduplication).  During de-deduplication, wildcards and/or
 # directories are *NOT* expanded to keep it simple. Therefore,
 # if the computed classpath has two specific mentions of
 # awesome-methods-1.0.jar, only the first one added will be seen.
 # If two directories are in the classpath that both contain
 # awesome-methods-1.0.jar, then Java will pick up both versions.

 # An additional, custom CLASSPATH. Site-wide configs should be
 # handled via the shellprofile functionality, utilizing the
 # hadoop_add_classpath function for greater control and much
 # harder for apps/end-users to accidentally override.
 # Similarly, end users should utilize ${HOME}/.hadooprc .
 # This variable should ideally only be used as a short-cut,
 # interactive way for temporary additions on the command line.
 # export HADOOP_CLASSPATH="/some/cool/path/on/your/machine"

 # Should HADOOP_CLASSPATH be first in the official CLASSPATH?
 # export HADOOP_USER_CLASSPATH_FIRST="yes"

 # If HADOOP_USE_CLIENT_CLASSLOADER is set, the classpath along
 # with the main jar are handled by a separate isolated
 # client classloader when 'hadoop jar', 'yarn jar', or 'mapred job'
 # is utilized. If it is set, HADOOP_CLASSPATH and
 # HADOOP_USER_CLASSPATH_FIRST are ignored.
 # export HADOOP_USE_CLIENT_CLASSLOADER=true

 # HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES overrides the default definition of
 # system classes for the client classloader when HADOOP_USE_CLIENT_CLASSLOADER
 # is enabled. Names ending in '.' (period) are treated as package names, and
 # names starting with a '-' are treated as negative matches. For example,
 # export HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES="-org.apache.hadoop.UserClass,java.,javax.,org.apache.hadoop."

 # Enable optional, bundled Hadoop features
 # This is a comma delimited list.  It may NOT be overridden via .hadooprc
 # Entries may be added/removed as needed.
 # export HADOOP_OPTIONAL_TOOLS="@@@HADOOP_OPTIONAL_TOOLS@@@"

 ###
 # Options for remote shell connectivity
 ###

 # There are some optional components of hadoop that allow for
 # command and control of remote hosts.  For example,
 # start-dfs.sh will attempt to bring up all NNs, DNS, etc.

 # Options to pass to SSH when one of the "log into a host and
 # start/stop daemons" scripts is executed
 # export HADOOP_SSH_OPTS="-o BatchMode=yes -o StrictHostKeyChecking=no -o ConnectTimeout=10s"

 # The built-in ssh handler will limit itself to 10 simultaneous connections.
 # For pdsh users, this sets the fanout size ( -f )
 # Change this to increase/decrease as necessary.
 # export HADOOP_SSH_PARALLEL=10

 # Filename which contains all of the hosts for any remote execution
 # helper scripts # such as workers.sh, start-dfs.sh, etc.
 # export HADOOP_WORKERS="${HADOOP_CONF_DIR}/workers"

 ###
 # Options for all daemons
 ###
 #

 #
 # Many options may also be specified as Java properties.  It is
 # very common, and in many cases, desirable, to hard-set these
 # in daemon _OPTS variables.  Where applicable, the appropriate
 # Java property is also identified.  Note that many are re-used
 # or set differently in certain contexts (e.g., secure vs
 # non-secure)
 #

 # Where (primarily) daemon log files are stored.
 # ${HADOOP_HOME}/logs by default.
 # Java property: hadoop.log.dir
 # export HADOOP_LOG_DIR=${HADOOP_HOME}/logs

 # A string representing this instance of hadoop. $USER by default.
 # This is used in writing log and pid files, so keep that in mind!
 # Java property: hadoop.id.str
 # export HADOOP_IDENT_STRING=$USER

 # How many seconds to pause after stopping a daemon
 # export HADOOP_STOP_TIMEOUT=5

 # Where pid files are stored.  /tmp by default.
 # export HADOOP_PID_DIR=/tmp

 # Default log4j setting for interactive commands
 # Java property: hadoop.root.logger
 # export HADOOP_ROOT_LOGGER=INFO,console

 # Default log4j setting for daemons spawned explicitly by
 # --daemon option of hadoop, hdfs, mapred and yarn command.
 # Java property: hadoop.root.logger
 # export HADOOP_DAEMON_ROOT_LOGGER=INFO,RFA

 # Default log level and output location for security-related messages.
 # You will almost certainly want to change this on a per-daemon basis via
 # the Java property (i.e., -Dhadoop.security.logger=foo). (Note that the
 # defaults for the NN and 2NN override this by default.)
 # Java property: hadoop.security.logger
 # export HADOOP_SECURITY_LOGGER=INFO,NullAppender

 # Default process priority level
 # Note that sub-processes will also run at this level!
 # export HADOOP_NICENESS=0

 # Default name for the service level authorization file
 # Java property: hadoop.policy.file
 # export HADOOP_POLICYFILE="hadoop-policy.xml"

 #
 # NOTE: this is not used by default!  <-----
 # You can define variables right here and then re-use them later on.
 # For example, it is common to use the same garbage collection settings
 # for all the daemons.  So one could define:
 #
 # export HADOOP_GC_SETTINGS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps"
 #
 # .. and then use it as per the b option under the namenode.

 ###
 # Secure/privileged execution
 ###

 #
 # Out of the box, Hadoop uses jsvc from Apache Commons to launch daemons
 # on privileged ports.  This functionality can be replaced by providing
 # custom functions.  See hadoop-functions.sh for more information.
 #

 # The jsvc implementation to use. Jsvc is required to run secure datanodes
 # that bind to privileged ports to provide authentication of data transfer
 # protocol.  Jsvc is not required if SASL is configured for authentication of
 # data transfer protocol using non-privileged ports.
 # export JSVC_HOME=/usr/bin

 #
 # This directory contains pids for secure and privileged processes.
 #export HADOOP_SECURE_PID_DIR=${HADOOP_PID_DIR}

 #
 # This directory contains the logs for secure and privileged processes.
 # Java property: hadoop.log.dir
 # export HADOOP_SECURE_LOG=${HADOOP_LOG_DIR}

 #
 # When running a secure daemon, the default value of HADOOP_IDENT_STRING
 # ends up being a bit bogus.  Therefore, by default, the code will
 # replace HADOOP_IDENT_STRING with HADOOP_xx_SECURE_USER.  If one wants
 # to keep HADOOP_IDENT_STRING untouched, then uncomment this line.
 # export HADOOP_SECURE_IDENT_PRESERVE="true"

 ###
 # NameNode specific parameters
 ###

 # Default log level and output location for file system related change
 # messages. For non-namenode daemons, the Java property must be set in
 # the appropriate _OPTS if one wants something other than INFO,NullAppender
 # Java property: hdfs.audit.logger
 # export HDFS_AUDIT_LOGGER=INFO,NullAppender

 # Specify the JVM options to be used when starting the NameNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # a) Set JMX options
 # export HDFS_NAMENODE_OPTS="-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=1026"
 #
 # b) Set garbage collection logs
 # export HDFS_NAMENODE_OPTS="${HADOOP_GC_SETTINGS} -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"
 #
 # c) ... or set them directly
 # export HDFS_NAMENODE_OPTS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"

 # this is the default:
 # export HDFS_NAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS"

 ###
 # SecondaryNameNode specific parameters
 ###
 # Specify the JVM options to be used when starting the SecondaryNameNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # This is the default:
 # export HDFS_SECONDARYNAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS"

 ###
 # DataNode specific parameters
 ###
 # Specify the JVM options to be used when starting the DataNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # This is the default:
 # export HDFS_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS"

 # On secure datanodes, user to run the datanode as after dropping privileges.
 # This **MUST** be uncommented to enable secure HDFS if using privileged ports
 # to provide authentication of data transfer protocol.  This **MUST NOT** be
 # defined if SASL is configured for authentication of data transfer protocol
 # using non-privileged ports.
 # This will replace the hadoop.id.str Java property in secure mode.
 # export HDFS_DATANODE_SECURE_USER=hdfs

 # Supplemental options for secure datanodes
 # By default, Hadoop uses jsvc which needs to know to launch a
 # server jvm.
 # export HDFS_DATANODE_SECURE_EXTRA_OPTS="-jvm server"

 ###
 # NFS3 Gateway specific parameters
 ###
 # Specify the JVM options to be used when starting the NFS3 Gateway.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_NFS3_OPTS=""

 # Specify the JVM options to be used when starting the Hadoop portmapper.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_PORTMAP_OPTS="-Xmx512m"

 # Supplemental options for priviliged gateways
 # By default, Hadoop uses jsvc which needs to know to launch a
 # server jvm.
 # export HDFS_NFS3_SECURE_EXTRA_OPTS="-jvm server"

 # On privileged gateways, user to run the gateway as after dropping privileges
 # This will replace the hadoop.id.str Java property in secure mode.
 # export HDFS_NFS3_SECURE_USER=nfsserver

 ###
 # ZKFailoverController specific parameters
 ###
 # Specify the JVM options to be used when starting the ZKFailoverController.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_ZKFC_OPTS=""

 ###
 # QuorumJournalNode specific parameters
 ###
 # Specify the JVM options to be used when starting the QuorumJournalNode.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_JOURNALNODE_OPTS=""

 ###
 # HDFS Balancer specific parameters
 ###
 # Specify the JVM options to be used when starting the HDFS Balancer.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_BALANCER_OPTS=""

 ###
 # HDFS Mover specific parameters
 ###
 # Specify the JVM options to be used when starting the HDFS Mover.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_MOVER_OPTS=""

 ###
 # Router-based HDFS Federation specific parameters
 # Specify the JVM options to be used when starting the RBF Routers.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_DFSROUTER_OPTS=""

 ###
 # HDFS StorageContainerManager specific parameters
 ###
 # Specify the JVM options to be used when starting the HDFS Storage Container Manager.
 # These options will be appended to the options specified as HADOOP_OPTS
 # and therefore may override any similar flags set in HADOOP_OPTS
 #
 # export HDFS_STORAGECONTAINERMANAGER_OPTS=""

 ###
 # Advanced Users Only!
 ###

 #
 # When building Hadoop, one can add the class paths to the commands
 # via this special env var:
 # export HADOOP_ENABLE_BUILD_PATHS="true"

 #
 # To prevent accidents, shell commands be (superficially) locked
 # to only allow certain users to execute certain subcommands.
 # It uses the format of (command)_(subcommand)_USER.
 #
 # For example, to limit who can execute the namenode command,
 # export HDFS_NAMENODE_USER=hdfs


 ###
 # Registry DNS specific parameters
 ###
 # For privileged registry DNS, user to run as after dropping privileges
 # This will replace the hadoop.id.str Java property in secure mode.
 # export HADOOP_REGISTRYDNS_SECURE_USER=yarn

 # Supplemental options for privileged registry DNS
 # By default, Hadoop uses jsvc which needs to know to launch a
 # server jvm.
 # export HADOOP_REGISTRYDNS_SECURE_EXTRA_OPTS="-jvm server"
	#
	# Licensed to the Apache Software Foundation (ASF) under one
	# or more contributor license agreements. See the NOTICE file
	# distributed with this work for additional information
	# regarding copyright ownership. The ASF licenses this file
	# to you under the Apache License, Version 2.0 (the
	# "License"); you may not use this file except in compliance
	# with the License. You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	# Set Hadoop-specific environment variables here.

	##
	## THIS FILE ACTS AS THE MASTER FILE FOR ALL HADOOP PROJECTS.
	## SETTINGS HERE WILL BE READ BY ALL HADOOP COMMANDS. THEREFORE,
	## ONE CAN USE THIS FILE TO SET YARN, HDFS, AND MAPREDUCE
	## CONFIGURATION OPTIONS INSTEAD OF xxx-env.sh.
	##
	## Precedence rules:
	##
	## {yarn-env.sh\|hdfs-env.sh} > hadoop-env.sh > hard-coded defaults
	##
	## {YARN_xyz\|HDFS_xyz} > HADOOP_xyz > hard-coded defaults
	##

	# Many of the options here are built from the perspective that users
	# may want to provide OVERWRITING values on the command line.
	# For example:
	#
	# JAVA_HOME=/usr/java/testing hdfs dfs -ls
	#
	# Therefore, the vast majority (BUT NOT ALL!) of these defaults
	# are configured for substitution and not append. If append
	# is preferable, modify this file accordingly.

	###
	# Generic settings for HADOOP
	###

	# Technically, the only required environment variable is JAVA_HOME.
	# All others are optional. However, the defaults are probably not
	# preferred. Many sites configure these options outside of Hadoop,
	# such as in /etc/profile.d

	# The java implementation to use. By default, this environment
	# variable is REQUIRED on ALL platforms except OS X!
	# export JAVA_HOME=

	# Location of Hadoop. By default, Hadoop will attempt to determine
	# this location based upon its execution path.
	# export HADOOP_HOME=

	# Location of Hadoop's configuration information. i.e., where this
	# file is living. If this is not defined, Hadoop will attempt to
	# locate it based upon its execution path.
	#
	# NOTE: It is recommend that this variable not be set here but in
	# /etc/profile.d or equivalent. Some options (such as
	# --config) may react strangely otherwise.
	#
	# export HADOOP_CONF_DIR=${HADOOP_HOME}/etc/hadoop

	# The maximum amount of heap to use (Java -Xmx). If no unit
	# is provided, it will be converted to MB. Daemons will
	# prefer any Xmx setting in their respective _OPT variable.
	# There is no default; the JVM will autoscale based upon machine
	# memory size.
	# export HADOOP_HEAPSIZE_MAX=

	# The minimum amount of heap to use (Java -Xms). If no unit
	# is provided, it will be converted to MB. Daemons will
	# prefer any Xms setting in their respective _OPT variable.
	# There is no default; the JVM will autoscale based upon machine
	# memory size.
	# export HADOOP_HEAPSIZE_MIN=

	# Enable extra debugging of Hadoop's JAAS binding, used to set up
	# Kerberos security.
	# export HADOOP_JAAS_DEBUG=true

	# Extra Java runtime options for all Hadoop commands. We don't support
	# IPv6 yet/still, so by default the preference is set to IPv4.
	# export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"
	# For Kerberos debugging, an extended option set logs more information
	# export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true -Dsun.security.krb5.debug=true -Dsun.security.spnego.debug"

	# Some parts of the shell code may do special things dependent upon
	# the operating system. We have to set this here. See the next
	# section as to why....
	export HADOOP_OS_TYPE=${HADOOP_OS_TYPE:-$(uname -s)}

	# Extra Java runtime options for some Hadoop commands
	# and clients (i.e., hdfs dfs -blah). These get appended to HADOOP_OPTS for
	# such commands. In most cases, # this should be left empty and
	# let users supply it on the command line.
	# export HADOOP_CLIENT_OPTS=""

	#
	# A note about classpaths.
	#
	# By default, Apache Hadoop overrides Java's CLASSPATH
	# environment variable. It is configured such
	# that it starts out blank with new entries added after passing
	# a series of checks (file/dir exists, not already listed aka
	# de-deduplication). During de-deduplication, wildcards and/or
	# directories are NOT expanded to keep it simple. Therefore,
	# if the computed classpath has two specific mentions of
	# awesome-methods-1.0.jar, only the first one added will be seen.
	# If two directories are in the classpath that both contain
	# awesome-methods-1.0.jar, then Java will pick up both versions.

	# An additional, custom CLASSPATH. Site-wide configs should be
	# handled via the shellprofile functionality, utilizing the
	# hadoop_add_classpath function for greater control and much
	# harder for apps/end-users to accidentally override.
	# Similarly, end users should utilize ${HOME}/.hadooprc .
	# This variable should ideally only be used as a short-cut,
	# interactive way for temporary additions on the command line.
	# export HADOOP_CLASSPATH="/some/cool/path/on/your/machine"

	# Should HADOOP_CLASSPATH be first in the official CLASSPATH?
	# export HADOOP_USER_CLASSPATH_FIRST="yes"

	# If HADOOP_USE_CLIENT_CLASSLOADER is set, the classpath along
	# with the main jar are handled by a separate isolated
	# client classloader when 'hadoop jar', 'yarn jar', or 'mapred job'
	# is utilized. If it is set, HADOOP_CLASSPATH and
	# HADOOP_USER_CLASSPATH_FIRST are ignored.
	# export HADOOP_USE_CLIENT_CLASSLOADER=true

	# HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES overrides the default definition of
	# system classes for the client classloader when HADOOP_USE_CLIENT_CLASSLOADER
	# is enabled. Names ending in '.' (period) are treated as package names, and
	# names starting with a '-' are treated as negative matches. For example,
	# export HADOOP_CLIENT_CLASSLOADER_SYSTEM_CLASSES="-org.apache.hadoop.UserClass,java.,javax.,org.apache.hadoop."

	# Enable optional, bundled Hadoop features
	# This is a comma delimited list. It may NOT be overridden via .hadooprc
	# Entries may be added/removed as needed.
	# export HADOOP_OPTIONAL_TOOLS="@@@HADOOP_OPTIONAL_TOOLS@@@"

	###
	# Options for remote shell connectivity
	###

	# There are some optional components of hadoop that allow for
	# command and control of remote hosts. For example,
	# start-dfs.sh will attempt to bring up all NNs, DNS, etc.

	# Options to pass to SSH when one of the "log into a host and
	# start/stop daemons" scripts is executed
	# export HADOOP_SSH_OPTS="-o BatchMode=yes -o StrictHostKeyChecking=no -o ConnectTimeout=10s"

	# The built-in ssh handler will limit itself to 10 simultaneous connections.
	# For pdsh users, this sets the fanout size ( -f )
	# Change this to increase/decrease as necessary.
	# export HADOOP_SSH_PARALLEL=10

	# Filename which contains all of the hosts for any remote execution
	# helper scripts # such as workers.sh, start-dfs.sh, etc.
	# export HADOOP_WORKERS="${HADOOP_CONF_DIR}/workers"

	###
	# Options for all daemons
	###
	#

	#
	# Many options may also be specified as Java properties. It is
	# very common, and in many cases, desirable, to hard-set these
	# in daemon _OPTS variables. Where applicable, the appropriate
	# Java property is also identified. Note that many are re-used
	# or set differently in certain contexts (e.g., secure vs
	# non-secure)
	#

	# Where (primarily) daemon log files are stored.
	# ${HADOOP_HOME}/logs by default.
	# Java property: hadoop.log.dir
	# export HADOOP_LOG_DIR=${HADOOP_HOME}/logs

	# A string representing this instance of hadoop. $USER by default.
	# This is used in writing log and pid files, so keep that in mind!
	# Java property: hadoop.id.str
	# export HADOOP_IDENT_STRING=$USER

	# How many seconds to pause after stopping a daemon
	# export HADOOP_STOP_TIMEOUT=5

	# Where pid files are stored. /tmp by default.
	# export HADOOP_PID_DIR=/tmp

	# Default log4j setting for interactive commands
	# Java property: hadoop.root.logger
	# export HADOOP_ROOT_LOGGER=INFO,console

	# Default log4j setting for daemons spawned explicitly by
	# --daemon option of hadoop, hdfs, mapred and yarn command.
	# Java property: hadoop.root.logger
	# export HADOOP_DAEMON_ROOT_LOGGER=INFO,RFA

	# Default log level and output location for security-related messages.
	# You will almost certainly want to change this on a per-daemon basis via
	# the Java property (i.e., -Dhadoop.security.logger=foo). (Note that the
	# defaults for the NN and 2NN override this by default.)
	# Java property: hadoop.security.logger
	# export HADOOP_SECURITY_LOGGER=INFO,NullAppender

	# Default process priority level
	# Note that sub-processes will also run at this level!
	# export HADOOP_NICENESS=0

	# Default name for the service level authorization file
	# Java property: hadoop.policy.file
	# export HADOOP_POLICYFILE="hadoop-policy.xml"

	#
	# NOTE: this is not used by default! <-----
	# You can define variables right here and then re-use them later on.
	# For example, it is common to use the same garbage collection settings
	# for all the daemons. So one could define:
	#
	# export HADOOP_GC_SETTINGS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps"
	#
	# .. and then use it as per the b option under the namenode.

	###
	# Secure/privileged execution
	###

	#
	# Out of the box, Hadoop uses jsvc from Apache Commons to launch daemons
	# on privileged ports. This functionality can be replaced by providing
	# custom functions. See hadoop-functions.sh for more information.
	#

	# The jsvc implementation to use. Jsvc is required to run secure datanodes
	# that bind to privileged ports to provide authentication of data transfer
	# protocol. Jsvc is not required if SASL is configured for authentication of
	# data transfer protocol using non-privileged ports.
	# export JSVC_HOME=/usr/bin

	#
	# This directory contains pids for secure and privileged processes.
	#export HADOOP_SECURE_PID_DIR=${HADOOP_PID_DIR}

	#
	# This directory contains the logs for secure and privileged processes.
	# Java property: hadoop.log.dir
	# export HADOOP_SECURE_LOG=${HADOOP_LOG_DIR}

	#
	# When running a secure daemon, the default value of HADOOP_IDENT_STRING
	# ends up being a bit bogus. Therefore, by default, the code will
	# replace HADOOP_IDENT_STRING with HADOOP_xx_SECURE_USER. If one wants
	# to keep HADOOP_IDENT_STRING untouched, then uncomment this line.
	# export HADOOP_SECURE_IDENT_PRESERVE="true"

	###
	# NameNode specific parameters
	###

	# Default log level and output location for file system related change
	# messages. For non-namenode daemons, the Java property must be set in
	# the appropriate _OPTS if one wants something other than INFO,NullAppender
	# Java property: hdfs.audit.logger
	# export HDFS_AUDIT_LOGGER=INFO,NullAppender

	# Specify the JVM options to be used when starting the NameNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# a) Set JMX options
	# export HDFS_NAMENODE_OPTS="-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=1026"
	#
	# b) Set garbage collection logs
	# export HDFS_NAMENODE_OPTS="${HADOOP_GC_SETTINGS} -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"
	#
	# c) ... or set them directly
	# export HDFS_NAMENODE_OPTS="-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:${HADOOP_LOG_DIR}/gc-rm.log-$(date +'%Y%m%d%H%M')"

	# this is the default:
	# export HDFS_NAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS"

	###
	# SecondaryNameNode specific parameters
	###
	# Specify the JVM options to be used when starting the SecondaryNameNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# This is the default:
	# export HDFS_SECONDARYNAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS"

	###
	# DataNode specific parameters
	###
	# Specify the JVM options to be used when starting the DataNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# This is the default:
	# export HDFS_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS"

	# On secure datanodes, user to run the datanode as after dropping privileges.
	# This MUST be uncommented to enable secure HDFS if using privileged ports
	# to provide authentication of data transfer protocol. This MUST NOT be
	# defined if SASL is configured for authentication of data transfer protocol
	# using non-privileged ports.
	# This will replace the hadoop.id.str Java property in secure mode.
	# export HDFS_DATANODE_SECURE_USER=hdfs

	# Supplemental options for secure datanodes
	# By default, Hadoop uses jsvc which needs to know to launch a
	# server jvm.
	# export HDFS_DATANODE_SECURE_EXTRA_OPTS="-jvm server"

	###
	# NFS3 Gateway specific parameters
	###
	# Specify the JVM options to be used when starting the NFS3 Gateway.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_NFS3_OPTS=""

	# Specify the JVM options to be used when starting the Hadoop portmapper.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_PORTMAP_OPTS="-Xmx512m"

	# Supplemental options for priviliged gateways
	# By default, Hadoop uses jsvc which needs to know to launch a
	# server jvm.
	# export HDFS_NFS3_SECURE_EXTRA_OPTS="-jvm server"

	# On privileged gateways, user to run the gateway as after dropping privileges
	# This will replace the hadoop.id.str Java property in secure mode.
	# export HDFS_NFS3_SECURE_USER=nfsserver

	###
	# ZKFailoverController specific parameters
	###
	# Specify the JVM options to be used when starting the ZKFailoverController.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_ZKFC_OPTS=""

	###
	# QuorumJournalNode specific parameters
	###
	# Specify the JVM options to be used when starting the QuorumJournalNode.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_JOURNALNODE_OPTS=""

	###
	# HDFS Balancer specific parameters
	###
	# Specify the JVM options to be used when starting the HDFS Balancer.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_BALANCER_OPTS=""

	###
	# HDFS Mover specific parameters
	###
	# Specify the JVM options to be used when starting the HDFS Mover.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_MOVER_OPTS=""

	###
	# Router-based HDFS Federation specific parameters
	# Specify the JVM options to be used when starting the RBF Routers.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_DFSROUTER_OPTS=""

	###
	# HDFS StorageContainerManager specific parameters
	###
	# Specify the JVM options to be used when starting the HDFS Storage Container Manager.
	# These options will be appended to the options specified as HADOOP_OPTS
	# and therefore may override any similar flags set in HADOOP_OPTS
	#
	# export HDFS_STORAGECONTAINERMANAGER_OPTS=""

	###
	# Advanced Users Only!
	###

	#
	# When building Hadoop, one can add the class paths to the commands
	# via this special env var:
	# export HADOOP_ENABLE_BUILD_PATHS="true"

	#
	# To prevent accidents, shell commands be (superficially) locked
	# to only allow certain users to execute certain subcommands.
	# It uses the format of (command)_(subcommand)_USER.
	#
	# For example, to limit who can execute the namenode command,
	# export HDFS_NAMENODE_USER=hdfs


	###
	# Registry DNS specific parameters
	###
	# For privileged registry DNS, user to run as after dropping privileges
	# This will replace the hadoop.id.str Java property in secure mode.
	# export HADOOP_REGISTRYDNS_SECURE_USER=yarn

	# Supplemental options for privileged registry DNS
	# By default, Hadoop uses jsvc which needs to know to launch a
	# server jvm.
	# export HADOOP_REGISTRYDNS_SECURE_EXTRA_OPTS="-jvm server"